Electromagnetic control device



y 26, 1938. w. H. BRUNS 2,125,150

ELECTROMAGNETIC CONTROL DEVICE Original Filed March 20, 1936 3 Sheets-Sheet l WM HIM/ 68W INVENTOR BY 'W ATTORNEY Jul 26; 1938. w. H. BRU N$ 2,125,150

ELECTROMAGNETIC CONTROL DEVI CE Original Filed March 20, 1936 3 Sheets-Sheet 2 y 6, 1938. w. H. BRUNS 2,125,150

ELECTROMAGNETIC CONTROL DEVICE Original Filed March 20, 1936 3 Sheets-Sheet 5 ATTORNEY Patented July 26, 1938 2,125,150. ELECTROMAGNETIC con'raor. DEVICE William Henry Bruns, 'Lincolndale, N. 1 assignor to Otis Elevator Company, New York, N. Y., a corporation of New Jersey Original application March 20, 1936, Serial No. 69,761. Divided and this application March 3, 1938, Serial No. 193,612

1 Claim.

The invention relates to control mechanism and especially to switching mechanism for protective purposes.

This application is a division of application Serial No. 69,761, filed March 20, 1936.

The invention involves the utilization of the combined effect of the fluxes in a plurality of magnetically interrelated flux paths of a relay to determine the amount of pull exerted on the relay armature.

The object of the invention is to provide a relay operating upon these principles, which is of simple construction, cheap to manufacture and reliable in operation.

In carrying out the invention, according to the preferred arrangement, the relay is provided with two operating coils. These coils are mounted on opposite legs of a closed core. The armature of the relay is arranged opposite a closed end of the core. The armature is moved toattracted position whenever the net resultant of the fluxes in the two legs passing between the core and the armature is above a certain amount. The coils are wound and connected in the circuits so that when certain conditions exist in the circuits, a net resultant flux is caused to flow between the core and the armature sufiicient to operate the relay. Under other conditions in the circuits, the net resultant flux is not sufiicient to move the armature toor hold it in attracted position. Flux not crossing the air gap between the core and armature circulates in the closed core.

Features and advantages of the invention will be apparent from the specification and appended claim.

The relay is useful for various purposes. It is of particular advantage for reverse phase and single phase protection of a motor. Application of the relay to a polyphase alternating current system to protect a motor against phase reversal and phase failure will be described.

In the drawings:

Figure 1 is a view in front elevation of a relay embodying the invention and associated equipment mounted on a panel;

Figure 2 is a view in section taken along the line 2-2 of Figure 1;

Figure 3 is a view, with parts omitted, in section taken along the line 3-3 of Figure 1;

Figure 4 is a section taken along the line 4-4 of Figure 3 with the coils of the relay shown in v dot and dash outline; and

phase motor against phase reversal and phase failure.

Referring to Figures 1, 2, 3 and 4 of the drawings, the relay, designated as a whole by the numeral Ill, comprises a movable armature ll supported on a magnet frame l2. Frame l2 comprises an upper horizontal portion I4 and a lower horizontal portion I5 joined by base portion l6. Frame I2 is secured at its base to an insulating panel I! by means of the screws I8. Screws l8 also serve to clamp a pair of vertically spaced blocks 20 of magnetic material between the base of the frame and the panel. The screws are countersunk in the base of the frame and pass through apertures in the blocks. Each of the blocks extends beyond the frame on each side thereof. A U-shaped core 25 is clamped at its open end between the endsof the blocks by means of screws 22. The legs 23 of the core extend horizontally outward from the panel on each side of the base iii. The yoke 2d of the core is positioned adjacent the armature l l. The upper horizontal portion M extends a slight distance beyond the yoke of the core. The armature engages portion it when in attracted position, thus providing an air gap between the armature and core. Core 25 comprises a plurality of laminations 25 secured between outer plates 26 as by rivets Tl. A pair of magnet coils 28 are mounted on core 2|, one on each leg 23. The legs 23, yoke 25 and blocks 26.) form a closed core for the magnet coils 28.

The armature is pivotally supported on lower horizontal portion is"; of the frame 92. To provide this support, the portion i5 is widened out and is formed with a pair of arms 38. The ends of the arms are formed with hook portions The armature is narrowed at the point where it is supported by portion it to enable it to be inserted between the arms 36 in back of the hook portions 32. The shoulders 33 thus formed on the armature rest on the arms so, thus providing a pivotal support for the armature. Between the arms 38, portion i5 is formed with an arcuate edge 3!. This edge provides a point contact for the face of the armature, which permits the on a rod 38 which extends through an aperture provided in the lower end o! the armature and through an aperture in the panel. The spring is mounted on the rod at the back of the panel and is held'under compression between cupshaped washers 37. A cotter pin 35 maintains the washer at the end of the rod in place. The end of the rod adjacent the armature is fiattened totprevent the rod pulling through the aperture in the armature. The outward pivotal movement of the armature is restricted by a stop so. The stop is riveted to the upper horizontal portion M of the frame and extends over into position to contact the 'back of the top edge of the armature when the armature is in unattracted position.

The relay is illustrated as provided with a pair of movable contacts ill for cooperation with a pair oi stationary contacts (12. Each stationary contact is carried by an elongated bracket 38 mounted on the panel. The outer and inner ends of the bracket are bentdownward at right angles. The contact point is secured in a hole drilled in the outer end of the bracket. The other end of the bracket is secured to the panel as by a screw 14 A tab 65 provided on the inner end of the bracket extends into an aperture in the panel. This prevents the bracket from turning on the panel.

The movable contacts G0 are carried by the armature. Each contact comprises a leaf spring 3d having a contact point secured in an aperture in the contacting end of the spring. ihe lower end of each spring is arranged in a slot (it provided in one side of a contact base 38. The con tact base is of insulating material and is secured to the armature below its hinge point by means of a screw 59, which is countersunk in the block. The armature is further narrowed at its lower end 86 and the base is provided with a groove iii which fits over the end 8 3 to locate the base on the armature. The bottom of each of the slots 6i slopes inwardly as shown in Figure 2. A spring guard 52 is also arranged in each slot. The springs are held against the bottoms of their respective slots and the spring guards are held against their respective springs by means of clips 53 and screws 55. The screws are countersunk in the back of the block and pass through holes provided in the clips. The nuts 55 for screws 5%, when tightened, press an angular end 56 of each clip against its respective spring guard, thereby securing the contact springs in place. The contacts may be bridged by a co nnector 57 secured to the screws 51% by nuts 58. Each spring guard extends upward from base 68 and is provided with a square shaped aperture 59 through which its respective contact spring extends. This arrangement prevents excessive flexing of the contact springs.

The armature is attracted by flux passing from the core through the armature and back to the core through the frame it. A shading coil 663 is provided to minimize noise when the armature is in attracted position. This coil is arranged on the upper portion id of the frame to take advantage of the leverage of the armature on the amount of pull which the shading coil produces. The outer end of portion id is slotted to receive the shading coil. To obtain a maximum efiect from the shading coil, a majority of the flux passing between the core and the armature, when the armature is in attracted position, is caused to return through the upper horizontal portion it of the frame. This isefiected by providinga slot ti across the face of the armature.

This slot is positioned so as to crowd the flux receivedby the armature from the core upwardly for return through upper portion is or the frame. In this way, the shading coil is subjected to a considerable amount of flux so that it is capable of exerting suficient pull on the armature to minimize any chatter. As illustrated, this slot is of an arcuate shape but other arra'ngents, such as a horizontal slot, may be employed. The action of the shading coil is augmented by the armature seating itself flatly against the edge of portion it due to the point contact of the ature at its hinge with the arcuate edge of the lower portion iii of the frame.

Impedance is utilized to control the prime relationship or the currents supplied to coiis 26.

An inductive reactance 68 and a resistance 86 are illustrated for this purpose. The inductance and resistance are mounted on panel ill. Binding posts 65 are provided on the panel t'or connecting the coils of the relay in the control circuits.

The-relay and its inductance and resistance have been illustrated as a unit provided on a separate panel portion. A cover 66 is provided ior this unit. The cover fits over and is supported by studs till, one at each corner of the panel. The cover is secured to the studs as by screws GE], which hit into tapped holes in the outer ends oil the studs. The other end d0 of each stud is threaded and extends through the panel. The panel may be mounted on cross bars M as shown in Figure 2. The panel is clamped to the bars at both the top and the bottom. Each clamp is formed by providing a nut if? on the threaded end iii of the stud to ciamp a clip i3 against the mounting bar.

In Figure 5 of the drawings, a schematic wiring diagram shows how the relay 66 as described above may be utilized to provide protection for a three phase alternating current motor against phase failure and phase reversal. The supply of current for the motor from the source is illustratedias controlled by switch 89. Switch 99 in turn is controlled by relay it). Li, L2 and L3 designate the alternating current supply mains, while the main line switch is designated as 86. The motor is designated as a whole as Gil. The operating coil 33 of switch hi is connected through contacts (ll, 62 of relay iii across supply lines L2 and LE When the contacts oi the relay are closed as shown, coil 83 of switch 88 is energized, causing the engagement of contacts 82 in the circuit for the motor. The opening of the contacts of the relay causes switch $6 to drop out.

Although relay it is illustrated as acting through switch iii to control the motor, it is to be understood that the contacts of relay it) may be located in a circuit common to the coils of .are for obtaining the desired phase and value of the currents supplied to the coils of the relay.

In operation, when main line switch 86 is closed, if the voltages of the supply mains are in proper phase rotation, the net resultant of the fluxes produced by the coils flowing to the armature is suficient to move the armature to attracted position. The armature, upon being 75 attracted, engages contacts ll, 42, energizing coil ll of switch Bl. Switch 8| in turn engages its contacts 82 in the circuit for the motor. Should the phase rotation be reversed at the time main line switch 84 is closed, the net resultant oi the fluxes produced by the coils flowing to the armature is not suflicient to move the armature to attracted position. Thus switch 8| is not energized. Should there be no voltage on one of the supply mains at the time switch 84 isclosed, there is substantially no resultant flux flowing to the armature so that the armature is not attracted.

Relay I0 is represented schematically in Figure 5 in order that the principles involved may be more readily understood. As before, the legs of the closed core are designated 23, the yoke 24 and the armature H. 86 designates the return path for the flux from the armature to the closed core. For convenience, this return path is shown as through the hinge for the armature but, as previously explained, the majority of the return flux is forced through the upper portion It of frame l2 when the armature is in attracted position.

The coils of the relay may-be wound so that current flow in the coils in the same direction with respect to junction point 90 or so that current flow in the coils in opposite directions with respect to point 90 produces a flux in each leg of the core in the same direction with respect to armature M. It will be assumed, for purposes of explanation, that the coils are wound so that flux is obtained in the two legs in the same direction with respect to the armature when current flows in the coils in the same direction with respect to point 9t. With the coils supplied with current from diiierent phases of a three phase alternating current source of supply, the portion of each alternating current cycle in which current flows in the same direction with respect to point 90 depends upon the manner in which the coils are connected to the supply lines and the value of inductance 63. To obtain operation of the relay as above described, the coils are connected to the supply mains in such way that with the voltages applied thereto in proper phase rotation, current flow in the coils in the same direction with respect to point 90 is obtained during the majority oi each alternating current cycle. In other words, the currents in the coils with respect to point 90 are in an assisting phase relationship, the actual phase reiationship being dependent on the value of inductance and resistance of the circuits. The flux produced by each coil being in phase with the current supplied to that coil, the fluxes in the two legs are in the same direction with respect to the armature during the majority of each alternating cycle. By proper selection of inductance and resistance values in the circuits, suificient flux is caused to fiow between the core and the armature during proper phase rotation to pull the armature to attracted position.

When the phase rotation of the voltages applied to the coils is reversed, current flow in each coil in the same direction with respect to point 90 is obtained only during a relatively small portion of each cycle. That is, the currents in the coils with respect to point 90 are in an opposing phase relationship, the actual phase relationship being dependent as before on the value of the inductance and resistance of the circuits, The values of inductance and resistance chosen are such that the net resultant flux which is caused to flow between the core and the armature during reverse phase rota-' tion is insuiilcient to pull the armature to attracted position.

When the currents supplied to the coils are in opposite direction with respect to point 90, the flux which does not pass between the core and armature circulates in the closed core.

When a phase failure occurs, the net resultant flux passing between the core and the armature is substantially zero so that no pull is exerted on the armature to pull it in. If either main Ll or main L3 is the one which fails, no current is supplied to one of the coils from the supply mains and no flux is produced by that coil. Therefore, there can be no flux in the leg on which that, coil is mounted in the same direction. with respect to the armature as the flux produced in the other leg by the energized coil thereon. In other words, there is no flux to oppose the flow of the flux created by the energized coil in the leg upon which the other coil is mounted so that the greater part of the flux created by the energized coil flows to this leg by way of the yoke 24, thereby circulating in the closed core instead of being forced across the air gap. Thus substantially no pull is exerted on the armature.

Should supply main L2 be the one which failed, both coils are placed in series across lines Li and L3 so that the same current passes through both coils. Under such conditions, the flow of current in the coils with respect to junction point 90 is opposite. Thus, the fluxes produced in the legs are always in opposite directions with respect to the armature under such conditions. The flux therefore circulates in the closed core instead of being forced across the air gap so that no pull is exerted on the armature. The total iiux is the same as when either line Li or line L3 fails as the voltage applied to each coil is halved.

Thus, it is seen that relay iii acts to protect the motor against reverse phase conditions, and also against phase failure regardless of which supply lines control switch Si is connected to.

Although the invention has been described as applied to an electromagnetic relay afiording reverse phase and single phase protection on a polyphase alternating current system, it is to be understood that the principles involved may be utilized for other devices, either in connection with alternating or direct current systems. For example, the invention may be embodied in a load relay in which one coil is wound as a current coil and is connected in series with the motor and the other coil is wound as a voltage coil and is connected so as to be subject to the voltage applied to the motor.

Many changes could be made in the above construction without departing from the scope of the invention. This includes not only varia tions in the constructional details of the relay but also changes in the flux paths or other changes which alter the manner in which the algebraic sum of fluxes is utilized to effect the operation of the relay. Condensive reactance may be utilized in controlling the phase relationships of the currents supplied to the coils of the relay, either in place of the inductive reactance or resistance or in combination therewith. It is therefore intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

A relay comprising; a U-shaped core disposed in a horizontal plane; two blocks of magnetizable material connecting the open end of said core to close said core; two coils, one on each leg of said core; a magnet frame having a base secured to said blocks and two branches extending horizontally from said base, one above and one below said core; an armature pivotaliy supported on said lower one of said branches for attraction by said core upon energization of said coils, flux produced in said core by said coils for attracting the armature returning to said core from said armature through said frame; and a shading 

